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has_filter( string $tag, callable|bool $function_to_check = false )

Check if any filter has been registered for a hook.

Parameters

$tag

(string) (Required) The name of the filter hook.

$function_to_check

(callable|bool) (Optional) The callback to check for.

Default value: false

Return

(false|int) If $function_to_check is omitted, returns boolean for whether the hook has anything registered. When checking a specific function, the priority of that hook is returned, or false if the function is not attached. When using the $function_to_check argument, this function may return a non-boolean value that evaluates to false (e.g.) 0, so use the === operator for testing the return value.

Source

File: wp-includes/plugin.php 

function has_filter( $tag, $function_to_check = false ) {
	global $wp_filter;

	if ( ! isset( $wp_filter[ $tag ] ) ) {
		return false;
	}

	return $wp_filter[ $tag ]->has_filter( $tag, $function_to_check );
}

Used By

Used By Description
wp-admin/includes/class-wp-site-health.php: WP_Site_Health::detect_plugin_theme_auto_update_issues()

Check for potential issues with plugin and theme auto-updates.
wp-admin/includes/class-wp-site-health.php: WP_Site_Health::check_wp_version_check_exists()

Test if wp_version_check is blocked.
wp-includes/ms-site.php: update_sitemeta_cache()

Updates metadata cache for list of site IDs.
wp-includes/blocks.php: do_blocks()

Parses dynamic blocks out of post_content and re-renders them.
wp-includes/blocks.php: _restore_wpautop_hook()

If do_blocks() needs to remove wpautop() from the the_content filter, this re-adds it afterwards, for subsequent the_content usage.
wp-includes/wp-db.php: wpdb::placeholder_escape()

Generates and returns a placeholder escape string for use in queries returned by ::prepare().
wp-includes/plugin.php: apply_filters_deprecated()

Fires functions attached to a deprecated filter hook.
wp-includes/customize/class-wp-customize-nav-menu-item-setting.php: WP_Customize_Nav_Menu_Item_Setting::preview()

Handle previewing the setting.
wp-admin/includes/class-wp-ms-sites-list-table.php: WP_MS_Sites_List_Table::column_plugins()

Handles the plugins column output.
wp-admin/includes/class-core-upgrader.php: Core_Upgrader::upgrade()

Upgrade WordPress core.
wp-admin/includes/class-wp-ms-sites-list-table.php: WP_MS_Sites_List_Table::get_columns()
wp-includes/capabilities.php: map_meta_cap()

Maps meta capabilities to primitive capabilities.
wp-includes/class-wp.php: WP::build_query_string()

Sets the query string property based off of the query variable property.
wp-includes/widgets/class-wp-widget-text.php: WP_Widget_Text::widget()

Outputs the content for the current Text widget instance.
wp-includes/class-wp-embed.php: WP_Embed::shortcode()

The do_shortcode() callback function.
wp-includes/plugin.php: has_action()

Check if any action has been registered for a hook.
wp-includes/meta.php: sanitize_meta()

Sanitizes meta value.
wp-includes/meta.php: register_meta()

Registers a meta key.
wp-includes/class-wp-editor.php: _WP_Editors::editor()

Outputs the HTML for a single instance of the editor.

Changelog

Version Description
2.5.0 Introduced.

© 2003–2019 WordPress Foundation
Licensed under the GNU GPLv2+ License.
https://developer.wordpress.org/reference/functions/has_filter